Bladed rotor of axial-flow fluid machine with means to retain blades in position on rotor



Sept. 5, 1961 L. HAWO H ET AL 2,998,959

BLADED ROTOR OF AXIAL- w FLUID MACHINE WITH MEANS T0 RETAIN BLADES INPOSITION ON ROTOR Filed Sept. 7, 1956 a Sheets-Sheet 1 Sept. 5, 1961 L.HAWORTH ET AL 2,998,959

BLADED ROTOR OF AXIAL-F FLUID MA ME! WITH MEANS TO RETAIN BLADESPOSITION ROTOR Filed Sept. 7, 1956 3 Sheets-Sheet 2 Sept. 5, 1961 L.HAWORTH ETAL 2,998,959

BLADED ROTOR 0F AXIAL-FLOW FLUID MACHINE WITH ME BLADES IN POSITION ONROTOR 5 Sheets-Sheet 5 6ANS TO RETAIN Filed Sept. 7, 195

United States Patent 2,998,959 BLADED ROTOR 0F AXIAL-FLOW FLUID MA-CHINE WITH MEANS TO RETAIN BLADES IN POSITION 0N ROTOR Lionel Haworthand James Alexander Petrie, Littleover, and Frederick Moss, Derby,England, assignors to Rolls-Royce Limited, Derby, England, a Britishcom- Filed Sept. 7, 1956, Ser. No. 608,458 Claims priority, applicationGreat Britain Sept. 29, 1955 7 Claims. (Cl. 25377) This inventionrelates to rotors of axial-flow fluid machines, such, for instance, asaxial-flow compressors and turbines, especially those of gas-turbineengines.

Such a rotor often comprises a disc carrying a ring of rotor blades atits periphery, the blades having shouldered root attachment portionswhich engage in correspondi-ngly'shaped generally-axial slots in the rimof the disc to retain the blades radially in position. Such a rotor willbe referred to as a rotor of the type described.

This invention has for an object to provide a simple construction ofmeans to prevent inadvertent disengagement of the blades from the discof a rotor of the type described.

According to this invention, in a rotor of the type described, the discis provided on an axially-facing surface of its rim with annularradially-inwardly-facing channel means coaxially with the rotor, theblade root attachment portions have radially-inwardly-facing channelswhich together form a substantially continuous annular channel coaxialwith the rotor and of greater radius than the annular channel means onthe rim, and there is provided means to retain the blades in position onthe rim comprising an annular plate adapted to be resilientlycontractable in diameter by provision of a gap at one side, said annularplate overlying axially-facing surfaces of the rim and attachmentportions and engaging in the uncontracted condition by an edge in thechannels in the attachment portions and by an annular flange thereonradially inwards of said edge in the annular channel means on the rim,thereby to be positioned relative to the disc and blade root attachmentportions and to retain the blade root attachment portions againstdisplacement in their slots.

Preferably, there is also provided means to prevent undesireddisengagement of the annular plate from the channels in the rim and inthe blades. In one preferred construction, this means comprisescircumferentiallyspaced radially-inwardly-extending lugs on the annularplate and correspondingly-spaced axial projections on the rim providingradial abutments for the lugs to prevent contraction of the annularplate, and a block extending circumferentially between a pair of thelugs and their associated projections and secured to the annular platethereby to prevent circumferential displacement of the annular plate;the block is conveniently positioned between lugs on the annular plateat each side of the gap therein and is secured to the annular plate by alocking pin passing through bores in the block and adjacent lugs. Inanother preferred construction, the means comprisescircumferentially-spaced axial projections on the disc andconespondingly-spaced radially-inwardly-projecting lugs on the platewhich are cut back opposite the projections to leave recesses which areoccupied by filler pieces, the latter having tabs which are bent up oneach side of the lugs to retain them in the recesses, and diametricallyopposite the gap in the plate a lug on the plate engaging between a pairof circumferentially-spaced projections on the disc.

- When the blade root attachment portions are of the kind providingbetween them passages through which a fluid could travel axially of therotor, the annular plate may also be employed to seal off the ends ofthe passages by lying fiat against the end surfaces of the rootattachment portions and the adjacent surface of the rim.

Two rotor constructions incorporating the invention will now bedescribed, the description referring to the accompanying drawings inwhich:

FIGURE 1 is an axial section through one construction of rotor,

FIGURE 2 is an enlarged view in the direction of arrow 2 in FIGURE 1,

FIGURE 3 is a view to a larger scale of pant of FIG- URE 2,

FIGURE 4 is a section on the line IV--IV of FIG- URE 3,

FIGURES 5 and 6 are axial views of two portions of the secondconstruction of rotor, the portion shown in FIG- URE 6 being located 180from the portion shown in FIGURE 5, and

FIGURE 7 is a section on the line VII-VII of FIG- URE 5 but drawn to alarger scale.

Referring to FIGURES 1 to 4, the rotor comprises a rotor disc 10 havingrim portion 11 whereon a ring of blades 12 are mounted.

Each blade 12 has a root attachment portion comprising a platform 13adjacent the operative part of the blade, 9. shouldered part 14,commonly known as a fir-tree root, to engage a correspondingly-shapedgenerally-axial slot 15 in the disc rim 11, and a stern portion 16 whichis circumferentially narrower than the platform 13 and the shoulderedpart 14 so that axial passages 17 are left be: tween the stem portions16. The part 14 of the root attachment portion has radially outwardlyfacing shoulders 14a and the slot 15 has cooperating radially inwardlyfacing shoulders 15a, these shoulders interengaging in abutment radiallyagainst one another to retain the blade radially in position.

The blades are provided with parts 18 in the form of tangs which abutthe upstream axially-facing surface of the rim 11 of the disc to preventdisengagement.

of the blades in one sense (to the right as seen in FIG- URE 1).

In order to retain the blades 12 against disengagement Each platform 13is formed along one edge with an:

axial extension 19 which is undercut with a radiallyduwardly-facinggroove 20. The grooves 20 together afford a substantially continuousgroove coaxial with the rotor.

The rim 11 is formed on its axially-facing surface 1-1b on the same sideof the rim as the grooves 20 and at a radius less than that of the slots15, with a continuous radially-inwardly-projecting flange 24 which formswith the rim 11 a radially-inwardly-facing channel 21, and radiallyinwards from the channel 21 the disc 10 is provided with a series ofcircumferentially spaced axial pro,- jections 22 of which two of saidprojections are closely adjacent projections 23. The parts of the rim 11which separate the blade slots 15 are provided, on the same side of therim as the groove 20, axial projections 11a having in this instance anaxial depth of .005" to .010".

A flat annular plate 25 is mounted on the rotor'to co-operate with thegrooves 20, channel 21 and projections 22, 23. The plate 25 is splitradially to provide a gap 26 bounded or defined by a pair of spacedradial1y-' extending edges 26b, and is resilient so that it can becontracted in diameter, and to facilitate this operation the lugs 32 canbe gripped by an appropriate tool.

The outer edge or the first edge of the plate 25 is blade platforms 13.v

The radially-inner part 29 of the plate 25 is axiallythickened and isformed with a radially-outwardly-dirested flange 30 which is of suchdiameter that, when the plate is uncontracted, the flange 30 occupiesthe channel 21.

The plate is also provided with radially-inwardlyprojecting lugs 31, 32corresponding in position and num her to the projections 22, 23, and thelugs and projections when radially aligned co-operate in abutment toprevent contraction of the plate 25. It is therefore apparent that theprojections 22, 23 on the disc and the lugs 31, 32 on the plate 25constitute radial abutment means to prevent undesirable contraction anddisengagement of the plate from the disc.

To assemble the plate to the disc, the plate is contracted to reduce thediameters of the bead 28 and flange 30 sufliciently to pass axiallyinside the extensions 19 and also the flange 24 bounding channels 20 and21 respectively, and the plate is offered up to the disc with the gap26, which is closed by the contraction, in the position indicated at Benin FIGURE 2 and thus'with the lugs 31, 32 in the positions shown at 31a,32a and offset from the projections 22, 23. The plate is now releasedfrom contraction so permitting the bead 28 to enter the groove formed bygrooves 20 and the flange 30 to enter channel 21. The projections 11a onthe rim 11 serve to spring the beaded edge 23 into good sealing contactwith the axial Wall 2011 of. the groove 20 on each blade. The plate 25is now rotated to the full line position with the lugs 31, 32 andprojections 22, 23 radially aligned.

To prevent rotation of the plate 25, a block 34 is provided to extendaxially and radially between the lugs 32 and projections 23, and theblock 34 is secured to the plate 25 by having a flange, similar toflange 30, which engages in the channel 21 in the disc and by means of awire pin 35 which passes through holes in the lugs 32 and the block 34',and has its ends bent over to prevent its detachment.

It will be noticed that for the purpose of maintaining the sealing ofthe passages 17 between the stems 16, the gap 26 in the plate 25 isarranged to extend along the end surface of one of the stems 16.

Referring now to FIGURES 5 to 7, in which the same reference numeralsare employed as'in FIGURES 1 to 4, to denote corresponding parts, thereis illustrated a construction in which the plate 25 can be presented tothe disc in the angular position it is to occupy. Inlthis construction,the plate is provided adjacent the gap 26 with a pair of lugs 132 whichare perforated at 132a to receive the contracting tool, and also aroundits inner edge with a series of circumferentially-spacedradially-inweirdly-extending lugs 131 the spacing of which is the sameas that of the projections 22 on the disc. The lugs 131 are cut backaxially to form recesses 131a in FIGURE 7 above the projections 22 topermit the lugs 131 on the plate to be passed over the projections whenthe plate is contracted in diameter for assembly. Also at a positiondiametrically opposite the gap 26, the plate 25 is provided a furtherradial lug 133 and the disc has at this position a pair ofcircumferentially-spaced projections 123 spaced by the width of the lug133. The lug 133 and projections 123 prevent-rotation of the plate inoperation, and facilitate positioning of the plate in assembly.

To assemble the plate to thedisc, the plate 25 is contracted in diameterand is presented axially to the disc in the appropriate angular positionto engage the lug 133 between the projections 123 and with the lugs 131angularly in line with the projections'22. The plate is now allowed toexpand so that its outer edge 28, which is preferably beaded as in theconstruction of FIGURES 1 to 4, engages in the grooves in the extensions19 of the platforms 13, its flange 30 being sprung into good sealingengagement with the walls of the channel 21 by the annular land 111a. Inorder to prevent accidental removal of the plate by contraction, fillerpieces-134 are 4 inserted in the recesses between the projections 22 andthe cut-back parts 131a of the lugs 131, and thin tabs 134a on thefiller pieces are bent up to lie on each side of the lugs 131 to retainthe filler pieces in position.

It will be appreciated that the combined locking and sealing plate ofthese constructions is simple in form and readily assembled and removed.

We claim:

1. A rotor of an axial-flow fluid machine, the rotor comprising a dischaving a rim with axially-facing surfaces, a plurality of blades, eachblade having a root attachment portion provided with radially-facingshoulders, a plurality of slots extending in said rim between i saidaxially-facing surfaces, each slot having radially facing shoulderscomplementary to the shoulders on the root attachment portions, saidshouldered root attachment portions of said blades being engaged in saidslots with radially-facing shoulders of the blades and slotsinterengaging to retain the blades radially in position, said rim havingadjacent one of said axially-facing surfaces an annularradially-inwardly-facing channel coaxial with the 1 rotor, saidshouldered root attachment portions having adjacent said one of theaxially-facing surfaces radiallyinwardly-facing grooves which having acircumferential extent together to forma substantially continuousannular groove coaxial with the rotor and of greater radius than saidannular radially-inwardly-facing channel, means to retain the blades inposition on the rim comprising an annular plate of resilient materialoverlying said one of the axially-facing surfaces of the rim and theroot attachment portions of the blades, said plate having a first edgeengaging the grooves in the root attachment portions and also havingthereon at a substantially smaller radius than said edge an annularflange engaging the annular radially-inwardly-facing channel on the rim,thereby to be positioned relative to the disc and root attachmentportions and to retain the root attachment portions against axialdisplacement in their slots, said plate being split radially at asingle' angular position to form a pair of spaced radially-extendingedges of the plate between which is a gap permitting contraction indiameter of the plate by closing the gap for engaging and disengagingthe said first edge in the grooves and the flange in the channel, andradial abutment means provided between said annular plate and the rimand operative to prevent undesirable contraction and disengagement ofthe annular plate.

2. A rotor as claimed in claim 1, wherein said radial abutment meanscomprises circumferentially-spaced radially-inWardly-extending lugs onthe annular plate, which lugs are cut back axially on theirradially-inner ends to define recesses with the rim of the disc,correspondinglyspaced axial projections on the rim of the disc at aradius less than said lugs and radially aligned with the recesses, andfiller pieces in said recesses extending radially between the cut backends of said lugs and said axial projections, said filler pieces havingtabs at their ends which are bent up on each side of the lugs to retainthem in the recesses; and comprising also means holding the annularplate against circumferential displacement comprising a lug on the plateat a position diametrically opposite the gap in the plate and a pair ofcircumferentially-spaccd projections on the disc, said lug on the plateengaging between said circumferentially-spaced projections.

3. A rotor as claimed in claim 1, wherein each of the blade rootattachment portions has a part engaging the rim and limiting movement ofthe blades relative to the rim in an axial direction towards said one ofthe axiallyfacing surfaces, and wherein an annular land is formedcoaxially with the rotor on said one of the axially-facing surfaces, andengages said annular plate to urge the plate into sealing engagementwith the sides of said grooves on the blade root attachment portions.

4. A rotor of an axial-flow fluid machine, the rotor comprising a dischaving a rim with axially-facing surfaces, a plurality of blades, eachblade having a root aasaees attachment portion provided withradially-facing shoulders, a plurality of slots extending in said rimbetween said axially-facing surfaces, each slot having radially facingshoulders complementary to the shoulders on the root attachmentportions, said shouldered root attachment portions of said blades beingengaged in said slots to retain the blades radially in position, saidrim having adjacent one of said axially-facing surfaces an annularradially-inWardly-facing channel coaxial with the rotor, said shoulderedroot attachment portions having adjacent said one of the axially-facingsurfaces radially-inwardlyfacing grooves which together form asubstantially continuous annular groove coaxial with the rotor and ofgreater radius than said annular radially-inwardly-facing channel, meansto retain the blades in position on the rim comprising an annular plateof resilient material overlying said one of the axially-facing surfacesof the rim and the root attachment portions of the blades, said platehaving a first edge engaging the grooves in the root attachment portionsand also having thereon at a substantially smaller radius than said edgean annular flange engaging the annular radially-inwardly-facing channelon the rim, there-.

by to be positioned relative to the disc and root attachment portionsand to retain the root attachment portions against displacement in theirslots, said plate being split radially to form a pair of spacedradially-extending edges of the plate between which is a gap permittingcontraction in diameter of the plate by closing the gap for engaging anddisengaging the edge in the grooves and the flange in the channel, anddisengagement-preventing means comprising circumferentially-spacedradially-inwardly-extending lugs on the annular plate andcorrespondingly-spaced axial projections on the rim providing radialabutments co-operating with the lugs to prevent undesirable contractionand disengagement of the annular plate.

5. A rotor as claimed in claim 4wherein disengagement-preventing meansalso comprise a block extending circumferentially between a pair of thelugs and their associated axial projections on the rim and secured tothe annular plate thereby to prevent circumferential displacement of theannular plate.

6. A rotor as claimed in claim 5, wherein the said pair of the lugs areprovided on the annular plate one at each side of the gap therein andthere is provided a locking pin passing through bores in the block andsaid pair of lugs and securing them together.

7. A rotor as claimed in claim 4, wherein each of the blade rootattachment portions has a part engaging the rim and limiting movement ofthe blades relative to the rim in an axial direction towards said one ofthe axiallyfacing surfaces, and wherein a substantially continuousannular land is formed coaxially with the rotor on said one of theaxially-facing surfaces, and engages said annular plate to urge theplate into sealing engagement with the side walls of said groove on theblade root attachment portions.

References Cited in the file of this patent UNITED STATES PATENTS2,755,062 Hill July 17, 1956 2,755,063 Wilkinson July 17, 1956 FOREIGNPATENTS 161,997 Australia Mar. 17, 1955 699,582 Great Britain Nov. 11,1953

